In mining, whether underground or surface mining (e.g. diamond mining, goldmining etc), once the mine has been formed, exploratory drill holes are typically then formed to try to locate ore bodies. These drill holes can have a length of up to 1 km bur are usually much shorter.
Initially, geologists will determine the likely location of an ore body or seam. The mine geologist will design the mine and the location of the exploratory holes and the surveyors will place survey markers in appropriate locations marking the intended hole positions. The survey markers will comprise a first mark on one wall of the mine and a second mark on an opposed wall of the mine. The markers are usually small reflective squares pinned to the mine wall. A “string line” between the two markers will show exactly the direction that the drilling apparatus will need to drill. This is known technology. For surface mines, a pair of pegs or markers inserted into the ground are typically used.
The direction typically includes the two components “elevation” and the “azimuth”. The elevation is the angle to the horizontal at which the drill rod is oriented and the azimuth is the degree or direction about a vertical axis that the drill rod is oriented.
Ensuring the correct “elevation” is usually not a great problem as the drill rig can quite easily be angled upwardly or downwardly to the correct elevation. However, ensuring the correct “azimuth” has been a problem to date and even a small error in the azimuth can cause rejection of the bore hole.
Once the survey markers have been completed, a drill rig is positioned to drill the required core samples. The drill rig is usually a very large self-propelled apparatus. A typical apparatus comprises a wheeled or tractor vehicle which has a forwardly extending boom arm and attached to the boom arm is a drill rig. The drill rig is attached to the boom arm such that it can adopt any required angle (in FIG. 1 the drill rig is pointing downwardly).
This type of apparatus is well-known and there are many different sizes and types of such apparatus, such as that illustrated in FIG. 3 for example which is an example of a skid-steered self-propelled rig.
Once the drill rig is roughly in position (determined by the survey markers), it needs to be very accurately adjusted to the survey markers. Once the adjustment is complete, the drill rig is secured in position and this is usually done by bolting the drill rig to the mine floor using a known type of feed frame positioner. For larger rigs, the weight of the rig can be sufficient to maintain the position.
The drill rig is then turned on to drill the required hole.
The present invention is directed to a laser unit device that can be used to very accurately correctly adjust the azimuth of the rig prior to bolting (securing) the rig into position. Preferably, the laser unit device is a gyroscopically aligned laser unit device.
Conventionally, string lines are used to align the rig prior to securement of the rig into position. That is, a string line is stretched between the survey markers on the opposed walls of the mine shaft. The apparatus is then positioned as close as possible to the string line and is aligned with the string line (that is the drill rig is aligned to be parallel with the string line to get the correct azimuth). Because of the size and shape of the apparatus, it is not possible to place the apparatus against the string line and usually the apparatus will be some distance away from the string line. For a “normal” sized apparatus, the apparatus will still be about 1 m away from the string line but for a larger apparatus, this can be between 3 to 4 m from the string line. A measuring tape is then used to accurately measure the distance between the front and the rear of the apparatus and the string line to ensure that the apparatus is exactly parallel with the string line such that when a hole is drilled, the hole will be at the correct azimuth.
In practice, it is difficult to obtain the level of accuracy that is demanded by the geologists using this known technique of string lines and measuring tapes. Once a pilot hole is collared, and it reaches its first survey mark (normally at approximately 5 to 15 meters) a survey tool is then inserted into the drilled hole. This survey tool normally provides a reading of both the elevation and the azimuth of the pilot hole. The driller then checks this against the hole plans and if not exactly correct, the hole will need to be redone.
The cost of drilling each hole can be many thousands of dollars and it is not unknown for the cost to be about $100,000 per hole. A drilling contractor is not paid for a “rejected” hole.
There is also a significant secondary issue once the rig has been properly aligned prior to drilling and that is maintaining the drill rod in the correct orientation and direction whilst drilling is taking place.
In the present specification, the term “drill rig” is not intended to be limiting and includes any type of drill or surface rig adapted to drill a hole in any type of mine including a surface or underground mine.
It will be clearly understood that, if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country.